Johnson made the remarks speaking on talk radio in Chicago, as reported by CNN.

“Again, I’m not gonna speak for John McCain — he has a brain tumor right now — that vote occurred at 1:30 in the morning, some of that might have factored in,” Johnson said.

McCain spokeswoman Julie Tarallo criticized Johnson’s remarks.

“It is bizarre and deeply unfortunate that Senator Johnson would question the judgment of a colleague and friend. Senator McCain has been very open and clear about the reasons for his vote,” she said in a statement.

McCain is undergoing treatment for the tumor back home in Arizona. After receiving his initial diagnosis in July, he flew back to Washington for the debate on the repeal-and-replace health care legislation. On the day he arrived, he cast a vote to proceed to debate, but he also delivered an impassioned speech on the floor outlining his concerns with the GOP proposal and how Congress got to it.

“We’ve tried to do this by coming up with a proposal behind closed doors in consultation with the administration, then springing it on skeptical members, trying to convince them it’s better than nothing, asking us to swallow our doubts and force it past a unified opposition. I don’t think that is going to work in the end. And it probably shouldn’t,” McCain said. “Why don’t we try the old way of legislating in the Senate, the way our rules and customs encourage us to act. If this process ends in failure — which seems likely — then let’s return to regular order.”

He later voted against the “skinny” repeal bill, joining two other GOP senators and all Senate Democrats, to defeat the legislation.